You can rasterize a SO and then later create a new SO from the resulting image/layer but the 2nd SO will NOT have any upstream editing, only downstream editing after making the 2nd SO. If you are wording about file size, I wonder if you really need to be making SO's? Exactly why are you using SO's?

Thanks for your reply. I'm converting a layer to a SO when I want to transform its image so I can make the image size appropriate to work in a collage. I load various images from LR into PS as layers and then convert whichever ones need to be transformed into SOs. I'm sorry but I don't understand what you mean by upstream vs. downstream editing.

I'm sorry but I don't understand what you mean by upstream vs. downstream editing.

A SO can be modified without actually effecting the "pixels" in the SO until you rasterize...so, while a SO, nothing degrades...but, once you rasterize the SO, if you make a 2nd SO, you'll have already rasterized the SO, a subsequent SO will have been modified and can not undo what has already been done upstream of the act of rasterizing...

Thanks again. I think I get it. So if I want to rasterize but also keep an "original" version of the image in the SO layer, then I should make a virtual copy of that image in LR and load the virtual copy into PS.